Electrophotographic composition of zinc oxide and a resin binder

ABSTRACT

The electrophotographic resin compositions disclosed herein comprise 10-96 mole percent of an acrylate ester having the formula CH2 C(R)COOR&#39;&#39;, wherein R is H, CH3 or C2H5 and R&#39;&#39; is an alkyl radical of the formula CnH2n 1 with n equal to 1-20, preferably 1-8; 0-86 mole percent of a vinyl monomer having the formula CH2 C(R&#39;&#39;&#39;&#39;&#39;&#39;)R&#39;&#39;&#39;&#39;&#39;&#39;&#39;&#39; wherein R&#39;&#39;&#39;&#39;&#39;&#39; is H or CH3 and R&#39;&#39;&#39;&#39;&#39;&#39;&#39;&#39; is an aryl radical of 6-12 carbon atoms, -CN or -OOCR&#39;&#39;&#39;&#39;&#39;&#39;&#39;&#39;&#39;&#39; wherein R&#39;&#39;&#39;&#39;&#39;&#39;&#39;&#39;&#39;&#39; is alkyl, cycloalkyl or aryl radical of 1-12 carbon atoms; 1-5 mole percent of an acrylic acid and 1-8 mole percent of an acrylamide or polymerizable amine compound. This electrophotographic resin composition is particularly suitable for use as a binder in preparing zinc oxide coatings for paper used in reproducing images with superior speed by an electrophotographic method.

llmted States Patent 1 [111 3,776,724 llsmani Dec. 4, 1973 [54] ELECTROPHOTOGRAPHIC COMPQSITION 2,893,977 7/1959 Suen et al. 260/8073 0 ZINC OXIDE AND A RESIN BINDER 3,404,979 10/1968 Boujour 96/1.8

[75] Inventor: Athar M. Usmani, Park Forest, 111.

[73] Assignee: The Sherwin-Williams Company,

Cleveland, Ohio [22] Filed: Sept. 22, 1971 [211 App]. No.2 182,854

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 84,102, Get 26,

1970, abandoned.

[52] U.S. Cl. 96/1.8, 96/l.5 [51] Int. Cl G03g 5/00 [58] Field of Search 96/l.8, 1.5

[56] References Cited UNITED STATES PATENTS 3,681,069 8/1972 McNamee et a.l. 96/l.8 X 3,649,263 3/1972 Tubuko et a1. 96/1.8 X 3,048,501 8/1962 Miller et a1. 117/155 3,481,735 12/1969 Graver 96/1.5 3,245,786 4/1966 Cassien et a1 96/1 2,653,140 9/1953 Wentworth et al. 260/8073 Primary Examiner-Norman G. Torchin Assistant Examiner-John L. Goodrow Attorney-Richard G. Smith et al.

[57] ABSTRACT The electrophotographic resin compositions disclosed herein comprise 10-96 mole percent of an acrylate ester having the formula CH =C(R)COOR', wherein R is H, CH or C 11 and R is an alkyl radical of the formula C H with n equal to 1-20, preferably l8; 0-86 mole percent of a vinyl monomer having the formula CH =C(R')R" wherein R' is 1-1 or CH and R" is an aryl radical of 6-12 carbon atoms, -CN or -OOCR"" wherein R"" is alkyl, cycloalkyl or aryl radical of l-l2 carbon atoms; l-5 mole percent of an acrylic acid and 1-8 mole percent of an acrylamide or polymerizable amine compound. This electrophotographic resin composition is particularly suitable for use as a binder in preparing zinc oxide coatings for paper used in reproducing images with superior speed by an electrophotographic method.

26 Claims, 4 Drawing Figures PATENTEDUEC 4197s 3,775 7 SHEET 10F 2 N In ATTORNEY PATENIEDuEc 4197a 3,776,724 SHEET 20F 2 9 2'-2.| FT.CANDLE-SEC. u 5.25 ,2.a FT. CANDLE-SEC. g 3.2 FT. CANDLE-SEC E Y O 4 3.5 2 m U 0! u] (L l.|.| L75 .4 O 2 ll|||I |l||l|lll MOLE PERCENT ACRYLAMIDE ISOILLUMINATE CONTOUR OF 0.46-0.56 MICROWATT-SEC. USING 360 MM LIGHT MOLE PERCENT ACRYLIC ACID l l I 525 7 0 INVENTOR.

MOLE PERCENT ACRYLAMIDE 4mm M USMAN,

Y l 5.2;. E B

A TTORNEY ELECTROPIIOTOGRAPHIC COMPOSITION OF ZINC OXIDE AND A RESIN BINDER This application is a continuation-in-part of copending application Ser. No. 84,102, filed Oct. 26, 1970, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to new electrophotographic resins suitable for use as binders in preparing zinc oxide electrophotographic coatings. More specifically, it relates to such coatings applied to paper for the reproduction of images by electrostatic deposition. 1

2. Related Prior Art In the electrophotographic recording and printing methods, it is necessary 'to have a surface which will accept and retain an electrostatic Charge for at least several minutes in the dark. Immediate exposure of the charged surface to actinic radiation causes dissipation of the charge from these areas.

ln carrying out an electrophotographic recording for reproducing an image, the entire photoconductive surface is given an electrostatic charge while protected against light. This is effected by friction, or, more commonly, by exposure to an electrical corona discharge. A pattern of actinic radiation is then applied to the charged surface, for example by exposure to actinicradiation through a transparency or by reflection from an image-bearing surface. This discharges the exposed areas, but leaves the unexposed areas still charged in the form of the image. Then the exposed surface is brought into contact with a powder which is attracted to the charged areas of the surface, preferablya powder which has a charge opposite to that of the charged areas of the latent image on the surface, but is not attracted to and is easily removed from the discharged areas of the surface.

In this wayan image is formed on the charged areas which may be transferred to another surface or may be heated and fused in situ on the areas of the original latent image. The surface to be used for such purposes must be very highly dielectric, non-conductive in the dark and will therefore hold an electrostatic charge for at least several minutes. The surface must be unaffected to any substantial extent by variations in moisture content of the surrounding atmosphere and must be free of conductive materials.

STATEMENT OF THE lNVENTION 7 a. -96, preferably 50-70 mole percent of an acrylate ester having the formula CH =CIR)COOR wherein R is H, CH or C l-l and R is an alkyl radical of the formula O l- 2:1 with n e c 1u alto" 120,- preferably l-8; b. 0-86, preferably -45 mole percent of a vinyl monomer having the formula CH =C(R' )R"" wherein R' is H or CH and R"" is an aryl radical of 61 2 carbon atoms, -CN or -OOCR""' wherein R"" is an alkyl, cycloalkyl or aryl radical of l] 2 carbon atoms;

. l-5, preferably 1.5-3 mole percent of a carboxylic acid-continaing monomer of an acrylic acid or anhydride, preferably selected from the class of v acrylic acid, methacrylic acid, ethacrylic acid, ma-

leic acid, fumaric acid, itaconic acid, R" half esters of itaconic, maleic and fumaric acids, crotonic acid, vinyl acetic acid, vinyl benzoic acid, alphachloroacrylic acid, alpha-phenylacrylic acid, and the like; and

d. l-l0, preferably 1.4-8 mole percent of a basic monomer of an amide-containing monomer or 1-10, preferably l-8 percent of an aminecontaining monomer.

Typical amide-containing monomers that are suitable include acrylamide, methacrylamide, ethacrylamide, alpha-chloroacrylamide, alpha-phenylacrylamide, diacetone acrylamide, etc.

The amine-containing monomer advantageously has an ionization constant in the range of 10 to 10' and may have a primary, secondary or tertiary amine group with the substituent groups preferably being alkyl groups of one-four carbon atoms. When the aminecontaining monomer is a vinyl pyridine, the preferrred proportion is l-3 mole percent, whereas with the other amines the preferred proportion is 26 mole percent.

Typical amine-containing monomers that are suitable include: t-butylaminoethyl methacrylate; diethylaminoethylmethacrylate; dimethylaminoethyl acrylate; dimethylaminoethyl methacrylate; 4-vinyl pyridine; ethylaminoethyl acrylate; diethylamino-trimethylene methacrylate; 3-vinyl pyridine; 2-vinyl pyridine; 2- methyl-S-vinyl pyridine; N-vinyl pyrrolidone; 5-ethyl-2- vinyl pyridine; 2-methyl-4-vinyl pyridine; 2-methyl-5- vinyl pyridine; paradimethylamino styrene; 2- aminopropyl vinyl ether; 2-aminoethyl vinyl ether; 6- aminohexyl acrylate; -aminohexyl acrylamide.

To produce a more flexible binder resin composition, the acrylate or methacrylate ester is preferably a mixture of two or more acrylates or methacrylates, such as methyl acrylate, methyl methacrylate,ethylacrylate, ethyl methacrylate, butyl methacrylate, amyl acrylate, 2-ethylhexyl acrylate, octyl methacrylate, propyl methacrylate, benzyl methacrylate, methyl ethacrylate, ethyl ethacrylate, butyl ethacrylate, octyl ethacrylate, heptyl acrylate, lauryl acrylate, stearyl methacrylate, decyl acrylate, tridecyl methacrylate, and the like.

Typical vinyl monomers suitable for the practice of this invention include styrene, vinyl toluene, vinyl xylene, ar-ethylstyrene vinyl naphthalene, vinyl methylnaphthalene, vinyl diphenyl, alpha-methylstyrene, isopropenyl toluene, isopropenyl naphthalene, isopropenyl diphenyl, acrylonitrile, methacrylonitrile, vinyl acetate, vinyl propionate, isopropenyl acetate, isopropenyl propionate, vinyl benzoate, vinyl octoate, and the like.

The carboxylic acid-containing monomer can be in the acid form or in its anhydride form during polymerization, but the anhydride, if used, is eventually hydrolyzed. Moreover, maleic anhydride or fumaric acid can be used in the copolymerization and eventually the resultant repeating unit esterified so as to give one acid group and one ester group in each repeating unit, or it can be amidified so as to give half acid and half amide. Or the half acid/half ester or half acid/half amide can be used as such in the original copolymerization. ln

such cases the molar proportions are calculated on the basis that half of the maleic or fumaric molecule is a mole of acid or a mole of amide, etc.

It is also contemplated that various functional groups can be added by post-reaction of a preformed polymer. For example in addition to the reaction cited above with maleic anhydride, it is also contemplated that a polymer containing an ethylol group such as hydroxy ethylated polyethyleneamine can be reacted with succinic anhydride to give repeating units having pendent groups containing free carboxylic acid groups.

The resin is prepared by the copolymerization of the aforenamed comonomers, preferably in a solvent such as toluene with the addition polymerization catalyzed by an initiator such as a free-radical generating catalyst. The methods and conditions for conducting the polymerizations are well known in the art and do not comprise any part of the present invention.

While various peroxides may be used for this purpose, the azo-type catalysts are preferred, such as azobisisobutyronitrile, 2,2'-azo-bis-2-ethyl-butyronitrile, and the like. Typical peroxy compounds that are suitable as polymerization catalysts include benzoyl peroxide, t-butyl peroxide, t-butyl perbenzoate, acetyl peroxide, lauryl peroxide, stearyl peroxide, phthallyl diperoxide, dicumyl peroxide, and the like.

The electrophotographic resin advantageously has a glass transition temperature (T,,) in the range of l5-30 C., preferably about 25 C. Its molecular weight should be in the range of 5,000-200,000, preferably l0,000-l00,000. Narrow molecular weight distribution is preferred.

The zinc oxide-resin composition is prepared by applying a solution of the resin, preferably in an aromatic solvent or a combination of aromatic solvent and an alkanol such as l-propanol, with a non-volatile content of 20-60%, preferably 40-50%, and generally a viscosity of 5-65 Stokes, to the zinc oxide and evaporating the solvent. The zinc oxide-resin binder components are advantageously used in the ratio of 1-20, preferably 5-l0 parts by weight of pigment per part of resin binder. 4

The zinc oxide suitable for the practice of this invention is the same type of finely divided zinc oxide presently used for electrophotographic purposes. Such materials are available commercially or may be prepared by sensitizing finely divided zinc oxide with various sensitizing dyes such as Eriochrome Black T, Bromophenol-B, Fluoresceine, a combination of Bromophenol-B and Fluoresceine, a combination of Bromophenol-B, F luoresceine and Brilliant Yellow 6G, a combination of Bromophenol-B and Alphazurine-2G, and the like. These sensitizing dyes are also available commercially. Other appropriate dyes for this purpose are disclosed in U.S. Pat. No. 3,052,540.

A coating thickness of 8-20, preferably ll-l3 micrometers is generally suitable for most purposes. The base may be paper, plastic, glass, wood, metal or other suitable material. Generally the amount of coating material ranges from 8 lbs. to lbs. per 3000 sq. ft. of coated area.

In addition to toluene, various other solvents can be used such as benzene, xylene, kerosene, or other highly aromatic commercial solvents. Aliphatic hydrocarbons can be present in the solvent but not in high enough proportion to interfere with the solvent power of the aromatic hydrocarbon. Sometimes an alkanol such as l-propanol is used to aid in achieving solubility of the acrylamide. Where longer chain acrylates or methacrylates are used, such as lauryl, stearyl, etc., aliphatic hydrocarbons in the solvent are more easily tolerated.

While applicant does not wish to be committed to any particular explanation or theory for the improved characteristics of the resin binder, it appears that the presence of both acid and amide or amine groups in the binder resin results in some kind of association which dramatically influences the electrical, photoconductive and printing properties of the resulting compositions. Advantageously, although a single acrylate or methacrylate may be used, a combination of a number of acrylates or methacrylates such as methyl methacrylate, butyl acrylate, butyl methacrylate, and others are preferred to balance each other in obtaining a more flexible resin.

The pigmentation or mixing of the oxide with the resin can be effected with various types of dispersion equipment such as ball mills, pebble mills, triple roll mills, sand mills, Cowles Dispersater, or any high impeller type equipment. Since the mixing is effected with quick wetting and formation of adsorbed layers, grinding aids are not required. Various dyes known in the art for that purpose are added to sensitize the oxide. The zinc oxide used is finely divided and of the sensitized type used in electrophotography. These are available commercially or finely divided zinc oxide can be sensitized by the addition of various sensitizing dyes as is known in the art. The amount of dye to be used corresponds to the amount presently being used for that purpose, generally about 0.05 to 0.25 percent of dye based on weight of zinc oxide.

Various commerical electrostatic machines may be used to evaluate the coatings and thereby the resin contained therein. An appropriate liquid toner suitable for this purpose is described in U.S. Pat. No. 3,399,140. By trial and error, the amount oflight is adjusted to get the best print for visual inspection. Resolution of lines in the photoprint, the black density of the print, background and the general quality of the print are determined by visual inspection.

The coatings may also be evaluated by a particular type of equipment designed for this purpose. A discharging light source is housed at the top of a light tunnel arranged vertically with a provision for a shutter at the bottom end. Vertically below this light tunnel an inductive probe is placed above a ground plate. This probe is designed to amplify the signals obtained from an electrostatic discharge and is connected to a highgain and high-input resistance amplifier. Signals from the amplifier are recorded by a suitable oscilloscope. A fiber optic connected to a photomultiplier tube is used and the output of the photomultiplier is used to trigger the oscilloscope. A specimen" of the oxide-resincoated paper, presubjected to a negative corona discharge is placed between theprobe and the ground plate. The equipment is encased to shut off outside light. The photodischarge profile is recorded by opening the shutter and allowing the light to strike and act on the specimen. Signals of dissipation of the charge from the specimen are then received on the screen oscilloscope and can be photographed.

FIG. 1 shows a schematic diagram of this equipment and FIG. 2 shows a profile plotted according to recordings from this equipment.

The photodischarge profile can be recorded at various wavelengths by inserting between the shutter and the specimen an appropriate optical filter. In this way, in addition to recordings for visible light, various wavelengths such as 360, 480, 580 and 610 nm can be applied and their effects on discharge recorded.

The profile is usually recorded as a bell-shaped curve of various widths depending upon the coating. It may be symmetrical and may even have humps or shoulders, depending on the characteristics of the coating. The peak of the curve is described as the time required for the specimen to discharge complete for a given light intensity. If the light intensity l is expressed in foot candle units and the time for complete discharge (t) in seconds, then light exposure will be 1 X t with units of foot candle-seconds. When the light intensity is expressed in microwatts/cm the light exposure will have units of microwattsecondlcm By obtaining profiles for visible light and for 360 nm, the analyses at 360 nm eliminates the role of the sensitizing effect of the ZnO and thus the performance of the resin is reflected.

FIG. 3 represents a light exposure diagram for visible light at various intensities shown as a function of acrylic acid and acrylamide proportions in the acrylic resins. The compositions of these resins are as shown in Example II. lsoilluminant expresses equal light exposure, and two distinct isoilluminant contours are found. The first contour is with light exposure of 2.0-2.1 foot candleseconds and is shown as the solid line in FIG. 3. The other contour is with light exposure of 2.8 foot candleseconds and is shown as the dotted line in FIG. 3. In the middle of both contours, a small contour or hole is obtained with 3.2 foot candle-seconds. Compositions represented by this area are slow and give prints with a dirty background. Good speed and prints of high quality, free of background, are obtained with the compositions represented by the area between the two (the solid and dotted) contours. Best results are obtained when the acrylic composition is represented by the area midway between the two contours.

FIG. 4 represents the light exposure diagram for 360 nm light as a function of the acrylic acid and acrylamide contents of the resim-The isoilluminant is 0.46-0.56 I

microwatt-second/cm Compositions inside the contour perform very well with alightwavelength of 360 nm. Similar light exposure diagrams for other wavelengths reveal the best composition or operable composition of this invention for the respective wavelengths. The visual print evaluation is in general accordance with the best compositions of acrylic acid and acrylamide contents or mole percentages represented by the contours.

In the drawings, FIG. 1 represents the apparatus described above for evaluating the oxide-resin coatings. Lamp 1 is suspended in housing 2 by means of supporting and supply means 1'. Shutter 3 is shown in the open position and is represented by 3 when in the closed position. The inductive probe 4 is positioned above ground plate 5 on which is placed the coated paper specimen 6 which is to be tested. Probe 4 is connected to a high gain, high input amplifier 7. Output of the amplifier is connected to oscilloscope 8 for the recording and display of the signal. Fiber optic 9 is connected to photomultiplier tube 10 and output of the photomultiplier tube is used to trigger the oscilloscope. When monochromatic light is to be used, filter 11 is introduced between the probe and the light housing. The oxide-resin coated paper is charged with a negative corona before it is placed on the ground plate. Amplifier 7 is turned on and shutter 3 is opened when the paper is ready for testing. The light discharge of the coating is plotted on the oscilloscope. A typical discharge graph is shown in FIG. 2, where discharge current I is plotted against 2,, or time in seconds.

The time to reach a peak 1,," as shown in the profile plotted in FIG. 2 is the time required for a given oxideresin smaple to discharge at 0 charge level for a given light intensity. In other words, for a fixed coating, t,, is a function of light intensity. If light intensity is measured in foot candles, then the total exposure required for the coating to discharge is light intensity (1) times 1,, in seconds. This gives exposure in foot candle-second units. If light intensity is measured in uw/cm, then ex posure required to discharge the coating is measured in uwsec./cm or ergs/cm The invention is illustrated by the following examples. These are presented merely for illustrative purposes and are not intended to restrict in any way the scope of the invention nor the manner in which it may be practiced. Parts and percentages are given by weight unless otherwise specified.

EXAMPLE I In a 5-liter reaction vessel equipped with stirrer, addition funnel, condenser and thermometer, 637 parts of toluene is charged and heated to C. under an inert gas blanket, such as nitrogen. A monomer-initiatorpropanol mixture is prepared consisting of 520 parts styrene, 480 parts butyl acrylate, 887 parts butyl methacrylate, 187.5 parts methyl methacrylate, 22.5 parts acrylic acid, 22.2 parts acrylamide, 10.6 parts of a20- bisisobutyronitrile and 425 parts of l-propanol. This mixture is added to the hot toluene over a period of 5 hours and the temperature of the reaction mass is maintained at 95 C. 1 2 C. during the period of addition and for an additional 8 hours. Towards the end of the heating period, the reaction mass is diluted with 1063 parts of toluene. The resulting solution has a nonvolatile content of 48.2% and the viscosity of the resin solution is 5.5 Stokes. This resin solution is mixed with zinc oxide pigment as described herein. Various dyes such as Fluorescein dye, Alizerin Light Green G. S., Eriochrome Black T or others known in the art as suitable for that purpose are added to sensitize the zinc oxide or titanium dioxide.

The resultant oxide resin composition is applied to paper as a coating having a thickness of 10-13 micrometers. The paper is allowed to dry rapidly in a hot blowing atmosphere and then allowed to adapt to darkness for 24 hours. When tested according to the methods described herein, the coated paper shows excellent electrophotographic properties.

EXAMPLE II Fourteen resin compositions are prepared using the procedure of Example I with identical conditions and in each case the basic composition comprises:

Styrene 2.0 Moles Butyl Acrylate l.5 Moles Butyl Methacrylate 2.5 Moles Methyl Methacrylate 0.75 Mole The amount of acrylic acid and acrylamide is varied in each case in accordance with the following table:

In order to achieve solubility of the acrylamide, lpropanol is used with the monomer mix in each case. The final solvent balance is 8 parts toluene and two parts l-propanol. The copolymerization is conducted by heating to 95 C. under an inert gas blanket (nitrogen) an initial charge of 637 parts of toluene. The monomer-initiator-propanol mixture is prepared consisting of 520 parts of styrene, 480 parts of butyl acrylate, 887 parts of butyl methacrylate, 187.5 parts methyl methacrylate, 10.6 parts of a20- bisisobutyronitrile and 25 parts of 1-propanol, and the appropriate amount of acrylic acid and acrylamide. (For example, for Resin 6, 22.5 parts of acrylic acid and 22.2 parts of acrylamide are used.) This mixutre is added to the hot toluene over a period of 5 hours with the temperature maintained at 95 C. i 2 C. This temperature is maintained for an additional eight hours and towards the end of this period it is diluted with 1063 parts toluene. (For Resin 6, the final percent nonvolatile content is 48.2 and the viscosity of the resin solution is 5.5 Stokes.)

ln preparing the coating formulation, the following amounts are used:

Zinc Oxide (photoconductivc pigment such as Photox 80 of New Jersey Zinc) Parts 471 1.5

Resin 1516.0 Toluene 3395.0 Ethanol 79.4 Methyl Cellosolve 58.0 Fluorcscein Dye 0.3 Alizarin Light Green G. S. 1.1 Eriochrome Black T 0,4 Methanol 238.3 Total Weight 10000.0

The zinc oxide pigment is ground in the resin solution with part of the toluene and ethanol in a sand mill. After grinding, the dispersion is adjusted for toluene according to the formula. Dye solutions in methyl cellosolve and methanol are added and mixed well to give the final coating composition. The coating is laid down on Kimberly Clark Paper 9515 with either a power driven or manual applicator. This can be a doctor blade or any other appropriate modification. A film thickness is applied to give a dry film in the range of -13 micrometers. After application of the wet coating, it is allowed to dry rapidly in a hot blowing atmosphere and the coated paper is then allowed to adapt to darkness for 24 hours. In testing, the coated paper is exposed to a negative corona and the charge measured with a simple electrometer with reference to a fixed plate. Papers are coated according to this procedure individually with the 14 resins prepared above in Example 11. These are tested with the specially designed equipment described above, and the results are plotted to give the curves shown in FIGS. 11] and IV.

8 EXAMPLE 111 The procedure of Example 1 is repeated using a temperature of 265 F. i 5 F. (130 C. i 3 C.) using the following amounts of materials:

Parts Mole Ratio Styrene 510 2.0 Butyl Methacrylate 887 2.5 Butyl Acrylate 480 1.5 Methyl Methacrylate 187.5 0.75 Acrylic Acid 45 0.25 Acrylamide 17.7 0.1 Azo-bisisobutyronitrile 6.3 Xylene (For resin preparation) I063 Xylene (for dilution) I063 The addition period is still 5 hours, but reaction after addition is completed is for 2 hours instead of eight hours. The resin solution viscosity of the product is 13 Stokes and the percent non-volatile is 47.8. This resin is used in a diazo coating formulation as follows:

Zinc Oxide (St. Joe

321 PC) Parts 3680 Resin 2684 Toluene 3213 Ethanol 359 Methanol 61.2 Eriochrome Black T 2.6 Crystal Violet 0.2 Total Weight 10000.0

The oxide-resin composition is tested in a commercial electrostatic copying machine and produces excellent images.

EXAMPLE lV Excellent image producing results are also obtained when the procedure of Example 111 is repeated using a reaction temperature of C. i 2 C. with the reaction continued for an additional 10 hours at that temperature after addition is completed. The resin solution has a 46.7 non-volatile content and a viscosity of 16 Stokes.

EXAMPLE V The various compositions prepared in Example 11 are tested under illumination with the equipment described in FIG. 1. Since the ZnO Photox 80 has a sensitizing peak at 360 nm and the sensitizing dyes have peaks at 480 nm, 580 nm and 610 nm, filters are used individually to give the corresponding monochromatic light, in addition to testing without the filters. The following table indicates the various results together with the moles of acrylic acid and acrylamide in the respective samples.

Moles Moles yw.-sec./cm. tit-- acrylle aeryl- Ft. ed

acid amide sec. 360 nm. 480 nm. 580 nm. 610 nm When tested for black density or contrast in printing, I

the compositions containing both' acrylamide and acrylic acid are graded at least good and in two cases excellent.

EXAMPLE v l The procedure of Example I is repeated using vinyl acetate as the major comonomer and using the following comonomer mixtures:

A B C D Vinyl acetate (moles 8.0 8.0 8.5 7.5 Methyl methacrylate (moles) 2.0 1.5 1.0 1.5 Butyl methacrylate (moles) 1.0 0.5 1.0 Ethyl acrylatc (moles) 1.0 0.5 1.0 0.5 Methacrylic acid (moles) 0.5 0.4 0.35 0.45 Acrylamide (moles) 0.5 0.4 0.5 0.4

Each polymerization is conducted at 70 C. 2 C. with the monomer addition being effected over a 6 hour period and polymerization continued for an additional 19 hours. The vinyl acetate is fed separately to the system from the mixture of other monomers and at a slightly faster rate because of its slower polymerization rate. The final solutions have a non-volatile content of 38-40 percent and the solvent is 8:2 of toluenezlpropanol. When tested in the zinc oxide coating for printing characteristics each resin shows the same improvements as noted in Example 1. Similar results are also obtained when the vinyl acetate is replaced with equivalent amounts respectively of vinyl propionate, isopropenyl acetate and vinyl octoate.

' Light exposure required for times with similar improvements in printing characteristics using the following variations in monomer components:

In a 5 liter reaction flask equipped with stirrer, addition funnel, condenser and thermometer, 1,428 g. of toluene is charged and heated to 100 C. 2 C. under an inert gas blanket. A monomer-initiator mixture is prepared consisting of 520.0 g. styrene, 710.0 g. butyl methacrylate, 640.0 g. butyl acrylate, 187.0 g. methyl methacrylate, 45.0 g. acrylic acid, 46.5 g. t-butyl aminoethyl methacrylate and 6.45 g.

. Speed unsatisfactory bisisobutyronitrile. This mixture is added to hot toluene over a period of five hours and the temperature of the reaction mass is maintained at C. i 2 C. during the period of addition and for an additional 15 hours. Towards the end of the holding period, the reaction mass is cut with 724.0 g. toluene. The resulting resin solution has a non-volatile content of 47.6%, the viscosity of the resin solution is 63 Stokes and the acid value is 16.0 mgm KOH per g. solid resin. A zinc oxide coating formulation is prepared as above in Example I1 and tested electrophotographically with the following results:

Lightexposure required for photo-discharge using visible light Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) wavelength 0.40 foot candle-sec.

0.138 microwatts seconds per cm Both speed and density in printing are excellent.

EXAMPLE [X The procedure of Example VIII is repeated using the following proportions of the'components;

704 grams for dilution 4 hours for addition;

25 hours for polymerization 22 Reaction temperature Reaction time Viscosity (Stokes) Nonvolatile material 47.5 Acid Value 16.4

Light exposure required for photo-discharge using visible light 0.96 foot candle-sec.

photo-discharge using ultraviolet I light of 380 nanometer (nm) wavelength 0.23 micrwatts-sec. per cm apparently due to absence of amine. v I

g v EXAMPLE x The procedure of Example VIII is repeated using the following proportions of the components:

Mole

Grams Ratio Mole Styrene 520 2.0 28.2 Butyl methacrylate 710 2.0 28.2 Butyl acrylate 640 2.0 28.2 Methyl methacrylate 187 0.75 10.6 Acrylic acid 45 0.25 3.52 Dimethylaminoethyl methacrylate 39.3 0.10 1.41

Azo bisisobutyronitrile Toluene 0.3% based on total monomer. 1072 g. initially and 1072 g. for dilution 5 hrs. for addition;

16 hrs. for polymerization Reaction temperature Reaction time Viscosity (Stokes) 22 Nonvolatile material 48.5 Acid value 14.7

Light exposure required for photo-discharge using visible light Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) 0.80 foot candle-see.

( 1 0.184 microwatts-sec. per cm (2) 0.136 microwatts-sec. per cm Both the speed and density in printing are excellent.

EXAMPLE XI The procedure of Example VIII is repeated using the following proportions of the components:

Mole

Grams Ratio Mole 7: Styrene 520 2.0 27.8 Butyl methacrylate 710 2.0 27.8 Butyl acrylate 640 2.0 27.8 Methyl methacrylate 187 0.75 10.4 Acrylic acid 45 0.25 3.47 Dimethylaminoethyl methacrylate 78.5 0.20 2.78

Azo-bisisobutyronitrile 0.37: based on total monomer Toluene 1457 g. initially and 726 g.

for dilution Reaction temperature 100 C.

Reaction time hrs. for addition; hrs.

for polymerization Viscosity (Stokes) 27 Z: Monvolatile Material Acid value Light exposure required for photodischarge using visible light 0.48 foot candle-sec. Light exposure required for photodischarge using ultraviolet light of 380 nanometer (nm) wavelength 0.101 microWatts-secJCm Both speed and density in printing are excellent.

EXAMPLE XII The procedure of Example VIII is repeated using the following proportions of the components:

Mole

Grams Ratio Mole Styrene 520 2.0 27.0 butyl methacrylate 710 2.0 27.0 Butyl acrylate 640 2.0 27.0 Methyl methacrylate 187 0.75 10.1 Acrylic acid- 45 0.25 3.38 Dimethylaminoethyl methacrylate 157 0.40 5.41

0.3% based on total monomer 1504 g. initially and 758 g. for dilution AZo-bisisobutyronilrlle Toluene 0.56 foot candle-sec.

0.101 microwatts-sec./cm

The speed and density in printing are excellent.

EXAMPLE XIII The procedure of Example VIII is repeated using the following proportions of the components:

Mole

Grams Ratio Mole 7P Styrene 2890 2.0 28.2 Butyl methacrylate 4932 2.5 35.2 Butyl acrylute 2668 1.5 21.1 Methyl methacrylate 1042 0.75 10.7 Acrylic acid 250 0.25 3.52 Dimethylaminoethyl methacrylate 218 0.10 1.41 Azo-bisisobutyronitrile 0.5% based on total monomer Toluene 12.030 g. initially Reaction temperature 100 C.

5 hrs. for addition; 5 hrs. for polymerization 13 Reaction time Viscosity (Stokes) Nonvolatile material Light exposure required for photo-discharge using visible light 0.96 foot candle-sec.

Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) wavelength 0.32 microwatts-secJcm' Both the speed and density in printing are excellent.

EXAMPLE XIV The procedure of Example VIII is repeated using the following proportions of the components:

Mole

Grams Ratio Mglefl; Styrene 510 2.0 2&6 Butyl methacrylate 887 2.5 35.7 Butyl acrylate 480 1.5 28.6 Methyl methacrylate 187 0.75 10.7 Acrylic Acid 45 0.25 3.57 Azo-bisisobutyronitrile 0.3% based on total monomer Xylene 1050 g. initially; 1050 g.

for dilution Reaction temperature 130" C.

5 hrs. for addition; 6 hrs. for polymerization 6.3

Reaction time Viscosity (Stokes) Nonvolatile material 46.3 Acid value 17.4

Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) wavelength Light exposure required for photo-discharge using visible light 0.40 microwatts-secJcm 1.20 foot candle-sec.

Speed in printing is unsatisfactory apparently due to absence of amine.

EXAMPLE XV The procedure of Example VIII is repeated using the following proportions of components:

Mole

Grams Ratio Mole Z Styrene S20 2.0 27.6 Butyl Methacrylate 710 2.0 27.6 Butyl acrylate 640 2.0 27.6 Methyl methacrylate 250 1.0 13.8 Acrylic acid -0- -0- -0- Dimethylaminoethyl methacrylate 98 0.25 3.45

Azo-bisisobutyronitrile 0.5% by weight based on total monomer Xylene 1115 g. initially and 1 g. for dilution Reaction temperature C.

Reaction time 4 hrs. for addition; 7 hrs.

for polymerization Viscosity (Stokes) 2 7r Nonvolatile material Light exposure required for photo-discharge using visible light Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) wavelength 1.12 foot candle-sec.

0.23 microwatts-secJcm Speed unsatisfactory apparently due to absence of acrylic acid.

EXAMPLE XVI The procedure of Example VIII is repeated using the following proportions of the components:

Mole Grams Ratio Mole Styrene 416 2.0 25.8 Butyl methacrylate 568 2.0 25.8 Butyl acrylate 512 2.0 25.8 Methyl methacrylate 300 1.5 19.4 Acrylic acid -0- -(l- -0- Dimethylaminoethyl methacrylate 78.5 0.25 3.23 Hydrochloric acid (36% Cone. in 100 g. propanol) 5 0.025

e uiv.

q Azobisisobutyronitrile 0.5% based on total monomer Xylene Reaction temperature Reaction time Viscosity (Stokes) Nonvolatile material Light exposure required for photo-discharge using visible light Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) wavelength 940 g. initially; 564 & 279 g. propanol for dilution 130 C.

4 hrs. for addition; 8 hrs. for polymerization 1.2 foot candle-sec.

0.235 rnicrowatts-sec./cm

Speed unsatisfactory due to absence of acrylic acid.

EXAMPLE XVll The procedure of Example Vlll is repeated using the 15 following proportions of the components:

Styrene Butyl methacrylatc Butyl acrylate Methyl methacrylate Acrylic acid t-Butylaminocthyl methacrylate Azobisisohutyronitrile Hydrochloric acid(367rin 100 g. propanol) Xylene Reaction temperature Reaction time Viscosity (Stokes) "/1. Nonvolatilc material Light exposure required for photo-discharge using visible light Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) wavelength Speed unsatisfactory apparently due to absence of acrylic acid.

Mole

Grams 4atio Mole% 0.5% based on total monomer 0.025 equiv.

947 g. initially; 568 g. & 279 g. propanol for dilution 130 C.

4 hrs. initially; 10 hrs. for polymerization 1.04 foot candle-sec.

0.299 rnicrowatts-see/cm EXAMPLE XVlll The'procedure ofExample Vlll is repeated using the following proportions of the components:

Styrene Butyl methacrylate Stearyl methacrylate Methyl mcthacrylate Acrylic acid t-Butylaminoethyl methacrylate Azohisisobutyronitrile Toluene Reaction temperature Reaction time Viscosity (Stokes) Nonvolatile material Acid value Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) wavelength Mole Grams Ratio Mole 520 2.0 29.5 1065 3.0 44.2 352.5 0.42 6.19 250 1.0 14.7 45 0.25 3.69 46.5 0.10 1.48

0.2% by wt. based on total wt. of monomer 1520 g. initially; 760 g. for dilution 5 hrs. for addition; hrs. for polymerization 0.020 microwatts'secJcm Speed and density in printing are excellent.

EXAMPLE XIX The procedure of Example Vlll is repeated using the following proportions of the components:

Styrene Butyl methacrylate Mole Grams Ratio Mole 624 2.0 29.9 1278 3.0 44.9

14 Stearyl methacrylate 423 0.42 6.29 Methyl methacrylate 300 1.0 15.0 Acrylic acid 54 0.25 3.74 Azobisisobutyronitrilc 0.2% based on total monomer Toluene 1340 g. initially; 1340 g.

for dilution 5 hrs. for addition; 14 hrs. for polymerization Reaction temperature Reaction time Viscosity (Stokes) Nonvolatile material Acid value Light exposure required for photo-discharge using ultraviolet light of 380 nanometer (nm) wavelength 0.825 microwatts-sec./ch

Speed unsatisfactory apparently due to absence of amine.

EXAMPLE xx The procedure of Example Vlll is repeated using the following proportions of the components:

Light exposure required for photodischarge using visible light Light exposure required for photodischarge using ultraviolet light of 380 nanometer (nm) wavelength 0.184 microwatts-secJcm 0.64 foot candle-sec.

Unsatisfactory density in printing apparently due to absence of acid.

EXAMPLE XXI Theprocedure of ExampleVlll is repeated using the following proportions of components:

Grams M'die'ltiiib Mole ll Styrene 364 2.0 27.8 Butyl methacrylate 497 2.0 27.8 Butyl acrylate 448 2.0 27.8 Methyl 'methacrylate 130 0.75 10.4 Acrylic acid 31 0.25 3.4 Z-Aminoethyl vinyl ether 60 0.20 2.8

Azobisisobutyronitrile Xylene 0.3% based on total monomer 1000 g. initially; 470 g. for

dilution 5 hrs. for addition; 10 hrs. for

polymerization Reaction temperature Reaction time Nonvolatile material Gives excellent speed and density.

EXAMPLE XXll The procedure of'Example Vlllis repeated using the following proportions of components:

Mole

. Grams Mole Ratio Mole Butyl Methacrylate 491 2.0 27 Butyl acrylate 443 2.0 27 Methyl methacrylate 475 2.75 37 Methacrylieacid 36 0.25 3.5 2-Aminoethyl vinyl ether 0.40 5.5 Azobisisobutyronitrile 0.3% based on total monomer Xylene 1000 g. for addition; 440 g. for

polymerization Reaction temperature Reaction time 5 hrs. for addition; l hrs. for

polymerization Nonvolatile material Gives excellent speed and density.

EXAMPLE XXIII The procedure of Example VIII is repeated using the following proportions of the components:

light exposure required for photodischarge using visible light Light exposure required for photodischarge using ultraviolet light of 380 nanometer (nm) wavelength 0.184 microwatts-secJcm 0.80 foot candle-sec.

Speed and density of printing are excellent.

EXAMPLE XXIV Two solutions are made from the following monomers:

Solution No. 1 Vinyl acetate Methyl acrylate t-Butylaminocthyl methacrylate l l. VAZO" 2. 82,0 2. Toluene l Vinyl acetate 8 Methyl acrylate t-Butylaminoethyl methacrylate VAZO B2 0, Azobisisohutyronitrile Solution No. 2

Solution No. l is charged into a liter flask fitted with heating mantle, cold water condenser and nitrogen blanket. This solution is heated to 158 F., at which time Solution No. 2 is added through a separatory funnel over a 5 hour period with the temperature maintained at l58 F.

After the addition of Solution No. 2 is completed the reaction is continued at the same temperature until an NVM of 66.6% is obtained. Then the resin is cut to 50% solids with 671.0 of toluene.

Final characteristics:

Viscosity 5.5 Stokes NVM 45.7%

Acid Value 4.l

Wt./Gallon 8.2 lbs. Color 1 Upon testing in a ZnO coating as in Example II it isfound that the light exposure required for photodischarge using ultraviolet light of 380 nanometers wavelength is: 0.080 microwatts-sec. per cm*.

While certain features of this invention have been described in detail with respect to various embodiments thereof, it will, of course, be apparent that other modifications can be made within the spirit and scope of this invention and it is not intended to limit the invention to the exact details shown above except insofar as they are defined in the following claims:

The invention claimed is:

1. An electrophotographic printing receptor comprising a base and a coating on said base comprising a major proportion of photosensitized, finely divided zinc oxide and a minor proportion in relation to said zinc oxide of a resin binder consisting essentially of a copolymer of:

a. 10 96 mole percent of an acrylate having the formula CH,=C(R)COOR, wherein R is H, CH or C ll, and R is an alkyl radical of the formula C,,H with n equal to l-20;

b. 0 86 mole percent ofa vinyl monomer having the formula CH =C(R" ')R"", wherein R is H or CH;, and R is an aryl radical of 6 12 carbon atoms, -CN or -OOCR"" wherein R"" is an alkyl, cycloalkyl or aryl radical of one l2 carbon atoms;

c. 1 5 mole percent ofa carboxylic acid monomer;

and

d. l 10 mole percent of a terminally ethylenically unsaturated polymerizable amine.

2. The electrophotographic printing receptor of claim 1 in which there is 50-70 percent of said acrylate, 30-45 percent of said vinyl monomer, 1.5-3 percent of said carboxylic acid-containing monomer and 1.4-6 percent of said polymerizable amine.

3. 'The receptor of claim 2 in which said vinyl monomer is vinyl acetate.

4. The receptor of claim 2 in which said vinyl monomer is styrene.

5. The receptor of claim 4 in which said carboxyic acid-containing monomer is selected from the class consisting of acrylic acid and methacrylic acid.

6. The printing receptor of claim 5 in which said sensitized zinc oxide is used in a proportion of 1.3-3 parts by weight per part by weight of said resin.

7. The printing receptor of claim 1 in which said polymerizable amine is t-butylaminoethyl methacrylate.

8. The printing receptor of claim 7 in which said carboxylic acid monomer is selected from the class consisting of acrylic acid and methacrylic acid.

9. The printing receptor of claim 8 in which said polymerizable amine represents about 2 percent of weight of said resin binder.

10. The printing receptor of claim 1 in which said polymerizable amine is dimethylaminoethyl methacrylate.

11. The printing receptor of claim 10 in which said carboxylic acid monomer is selected from the class consisting of acrylic acid and methacrylic acid.

12. The printing receptor of claim 11 in which said polymerizable amine represents about 2 percent by weight of said resin binder.

13. The printing receptor of claim 1 in which said polymerizable amine is vinyl pyridine.

14. The printing receptor of claim 13 in which said carboxylic acid monomer is selected from the class consisting of acrylic acid and methacrylic acid.

15. The printing receptor of claim 14 in which said vinyl pyridine represents about 1 percent by weight of said resin binder.

16. The printing receptor of claim 1 in which said polymerizable amine is 2-aminoethyl vinyl ether.

17. The printing receptor of claim 16 in which said carboxylic acid monomer is selected from the class consisting of acrylic acid and methacrylic acid.

18. The printing receptor of claim 1 in which the mole proportions of said carboxylic acid-containing monomer and of said polymerizable amine have values coming within the area defined by and between the isoilluminant contours shown in FIG. 3 for 2-2.2 foot candle-seconds and 2.8 foot candle-seconds.

19. The printing receptor of claim ,18 in which said carboxylic acid-containing monomer is acrylic acid and said polymerizable amine is t-butylaminoethyl methacrylate.

20. The printing receptor of claim 18 in which said carboxylic acid-containing monomer is selected from the class consisting of acrylic acid and methacrylic zinc oxide is sensitized by a dye selected from the class consisting of Eriochrome Black T, Bromophenol-B, Fluoresceine, Brilliant Yellow 66 and Alphazurine-2G. 24. The printing receptor of claim 1 in which s aid vinyl monomer is a vinylaryl compound.

25. The printing receptor of claim 1 in which said vinyl monomer is styrene.

26. The printing receptor of claim 25 in which there i is 30-45 mole percent of styrene.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,776,72Lt Dated December L 1973 Inventor-(5) Athar M. Usmani It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 61, correct CH =CIR)COOR to read -CH =C(R)COOR' Column 2, line 2, correct R to read R Column 16, line 36, correct "carboxyic" to read carboxylic Column 16, line Lt), correct "of" to read by Signed and sealed this 25th day of June 197L| (SEAL) Attest':

EDWARD M.FLETCHER,JR. C. MARSHALL DANN Attesting Officer 7 Commissioner of Patents USCOMM-DC 60376-P69 u.s. GOVERNMENT PRINTING OFFICE: 1569 0-366-334.

: ORM PO-105O (10-69) 

2. The electrophotographic printing receptor of claim 1 in which there is 50- 70 percent of said acrylate, 30-45 percent of said vinyl monomer, 1.5-3 percent of said carboxylic acid-containing monomer and 1.4-6 percent of said polymerizable amine.
 3. The receptor of claim 2 in which said vinyl monomer is vinyl acetate.
 4. The receptor of claim 2 in which said vinyl monomer is styrene.
 5. The receptor of claim 4 in which said carboxyic acid-containing monomer is selected from the class consisting of acrylic acid and methacrylic acid.
 6. The printing receptor of claim 5 in which said sensitized zinc oxide is used in a proportion of 1.3-3 parts by weight per part by weight of said resin.
 7. The printing receptor of claim 1 in which said polymerizable amine is t-butylaminoethyl methacrylate.
 8. The printing receptor of claim 7 in which said carboxylic acid monomer is selected from the class consisting of acrylic acid and methacrylic acid.
 9. The printing receptor of claim 8 in which said polymerizable amine represents about 2 percent of weight of said resin binder.
 10. The printing receptor of claim 1 in which said polymerizable amine is dimethylaminoethyl methacrylate.
 11. The printing receptor of claim 10 in which said carboxylic acid monomer is selected from the class consisting of acrylic acid and methacrylic acid.
 12. The printing receptor of claim 11 in which said polymerizable amine represents about 2 percent by weight of said resin binder.
 13. The printing receptor of claim 1 in which said polymerizable amine is vinyl pyridine.
 14. The printing receptor of claim 13 in which said carboxylic acid monomer is selected from the class consisting of acrylic acid and methacrylic acid.
 15. The printing receptor of claim 14 in which said vinyl pyridine represents about 1 percent by weight of said resin binder.
 16. The printing receptor of claim 1 in which said polymerizable amine is 2-aminoethyl vinyl ether.
 17. The printing receptor of claim 16 in which said carboxylic acid monomer is selected from the class consisting of acrylic acid and methacrylic acid.
 18. The printing receptor of claim 1 in which the mole proportions of said carboxylic acid-containing monomer and of said polymerizable amine have values coming within the area defined by and between the isoilluminant contours shown in FIG. 3 for 2-2.2 foot candle-seconds and 2.8 foot candle-seconds.
 19. The printing receptor of claim 18 in which said carboxylic acid-containing monomer is acrylic acid anD said polymerizable amine is t-butylaminoethyl methacrylate.
 20. The printing receptor of claim 18 in which said carboxylic acid-containing monomer is selected from the class consisting of acrylic acid and methacrylic acid.
 21. The printing receptor of claim 18 in which said polymerizable amine is dimethylaminoethyl methacrylate.
 22. The printing receptor of claim 1 in which said base is paper.
 23. The printing receptor of claim 1 in which said zinc oxide is sensitized by a dye selected from the class consisting of Eriochrome Black T, Bromophenol-B, Fluoresceine, Brilliant Yellow 6G and Alphazurine-2G.
 24. The printing receptor of claim 1 in which s aid vinyl monomer is a vinyl aryl compound.
 25. The printing receptor of claim 1 in which said vinyl monomer is styrene.
 26. The printing receptor of claim 25 in which there is 30-45 mole percent of styrene. 